Predator detection and avoidance by starlings under differing scenarios of predation risk |
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Authors: | Devereux Claire L; Whittingham Mark J; Fernandez-Juricic Esteban; Vickery Juliet A; Krebs John R |
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Institution: | a Edward Grey Institute of Field Ornithology, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK, b School of Biology, Ridley Building, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, UK, c Department of Biological Sciences, California State University, Long Beach, 1250 Bellflower Blvd, Long Beach, CA 90840-3702, USA, and d British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU, UK |
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Abstract: | Practically all animals must find food while avoiding predators.An individual's perception of predation risk may depend on manyfactors, such as distance to refuge and group size, but it isunclear whether individuals respond to different factors ina similar manner. We tested whether flocks of foraging starlingsresponded in the same way to an increased perception of predationrisk by assessing three factors: (1) neighbor distances, (2)habitat obstruction, and (3) recent exposure to a predator.We found that in all three scenarios of increased risk, starlingsreduced their interscan intervals (food-searching bouts), whichincreased the frequency of their vigilance periods. We thenexamined how one of these factors, habitat obstruction, affectedescape speed by simulating an attack with a model predator.Starlings were slower to respond in visually obstructed habitats(long grass swards) and slower when they had their head downin obstructed habitats than when they had their head down inopen habitats. In addition, reaction times were quicker whenstarlings could employ their peripheral fields of vision. Ourresults demonstrate that different sources of increased riskcan generate similar behavioral responses within a species.The degree of visibility in the physical and social environmentaffects both the actual and perceived risk of predation. |
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Keywords: | interscan interval predation risk starlings vigilance visibility vision |
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